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| Book/Report | FZJ-2018-01777 |
; ;
1981
Kernforschungsanlage Jülich, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/17619
Report No.: Juel-1746
Abstract: An application of the Linear programming to the evaluation of impurity flux is demonstrated, in an attempt to obtain more conelusive information on the impurity transport mechanism. This gives a better insight to the accuracy required in the rate coefficients an one hand and in the experimental profiles on the other hand, if clearcut information concerning the diffusion rates is to be obtained from the quasi-steady impurity profiles in tokamak plasmas. The behavior of Fe XXIII in PLT is taken as an example. If the uncertainties in the rate coefficients in the continuity equation are smaller than a factor of two, it is found that the flux $\Gamma_{c,e}$ of Fe XXIII, evaluated from the continuity equation, can never be made to calneide with the neoclassical flux, $\Gamma_{n,c}$. In the region, r $\le$ 15 centimeters, $\Gamma_{c,e}$ can only be restricted to values within the limits ±16 times $\Gamma_{n.c}$, or harmonically, 30 and (1/30) times the latter. A set of "optimum" values for the rate coefficients, which yields the pese values corresponding to each of these two cases nearest to $\Gamma_{n.c}$ are computed. The density profiles of Fe XXIII are then evaluated from the continuity equation, using these "optimum " values of rate coefficients, the experimental profiles of Fe XXII and Fe XXIV and assuming that the transport mechanism is purely neoclassical. The differente between these profiles and those observed experimentally is an the average, roughly 15 % this indicates that a high degree of accuracy is required in measuring the impurity densities, if one wishes to conelude whether the flux is neoclassical or not in this case.
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